Air compressors come in varying configurations, for example, screw compressors and piston compressors. Air is compressed and delivered by hoses to one or more air tools, for example, pneumatic drills, staple guns and other pneumatically driven devices. These tools contain an air motor which is powered by the pressurised air source from the air compressor. The air motor produces exhaust air which is vented to ambient air. The escape of exhaust air is noisy. The air compressor will not usually support sustained use of the air tool because of the resulting pressure drop.
It has been proposed in German Patent Application No. 24 10 832 to have the exhaust air from a compressed air tool recycled under pressure to the intake side of the air compressor via an auxiliary pressure vessel. The disclosure includes a large number of components including piping, valves and gauges which must be fitted to an existing air compressor. The compressed air return line from the auxiliary pressure vessel is connected to only one cylinder of a multiple piston-type air compressor. The auxiliary pressure vessel buffers the returning exhaust air. This proposal is impractical, in use, because of the bulk of an auxiliary tank and the additional components needed to operate the system.
In published Japanese Patent Application No. 2002-174203 an air actuator system is disclosed. This application illustrates the use of air actuators for an air press rather than air motors. The intake of the compressor creates a vacuum on the exhaust side of the air actuators rather than an air boost. The preferred embodiments show the use of multiple actuator valves and electronics to control the system.